1. Field of the Invention
The present invention relates to a multilayer electronic component and a method for manufacturing the same, and more particularly to a multilayer electronic component formed by plating external electrodes directly on external surfaces of a laminate and to a method for manufacturing the multilayer electronic component.
2. Description of the Related Art
As shown in FIG. 4, a multilayer electronic component 101, which is represented by a multilayer ceramic capacitor, generally includes a laminate 105 including a plurality of insulating layers 102 laminated to each other and a plurality of layer-shaped internal electrodes 103 and 104 provided along interfaces between the insulating layers 102. At end surfaces 106 and 107 of the laminate 105, edges of the internal electrodes 103 and 104 are exposed, respectively, and external electrodes 108 and 109 are provided to electrically connect the edges of the internal electrodes 103 and 104, respectively.
When the external electrodes 108 and 109 are formed, in general, paste electrode films 110 are first formed by applying a metal paste containing a metal component and a glass component on the end surfaces 106 and 107 of the laminate 105, followed by firing. Next, on the paste electrode films 110, first plating layers 111 containing Ni or other suitable material as a primary component are formed, and furthermore, on the first plating films, second plating films 112 containing Sn or other suitable material as a primary component are formed. That is, each of the external electrodes 108 and 109 have a three-layer structure including the paste electrode film 110, the first plating film 111, and the second plating film 112.
The external electrodes 108 and 109 must have superior wettability to solder when the multilayer electronic component 101 is mounted on a substrate using solder. At the same time, the external electrode 108 must electrically connect the internal electrodes 103 which are in an electrically insulated state, and the external electrode 109 must electrically connect the internal electrodes 104 which are in an electrically insulated state. The second plating film 112 ensures the solder wettability, and the paste electrode films 110 electrically connect the respective internal electrodes 103 and 104. The first plating film 111 prevents solder leaching during solder bonding.
However, the paste electrode film 110 has a relatively large thickness, such as several tens to several hundreds micrometers. Thus, when the dimensions of this multilayer electronic component 101 are set within a predetermined standard value, an effective volume to ensure an electrostatic capacity must be decreased by an amount corresponding to that required to ensure the volume of the paste electrodes 110. On the other hand, since the thickness of each of the plating films 111 and 112 is approximately several micrometers, if each of the external electrodes 108 and 109 can be only with the first plating film 111 and the second plating film 112, a larger effective volume for the electrostatic capacity can be provided.
For example, Japanese Unexamined Patent Application Publication No. 63-169014 disclose a method for depositing a conductive metal layer by electroless plating so that internal electrodes exposed at one side wall surface of a laminate are short-circuited to the entire side wall surface at which the internal electrodes are exposed.
However, in the method disclosed in Japanese Unexamined Patent Application Publication No. 63-169014, since the bonding between the internal electrodes and the plating film is insufficient, moisture and other contaminants are disadvantageously likely to enter the laminate. Thus, when a loading test is performed under high-temperature and high-humidity conditions, the life of a multilayer electronic component is likely to be reduced.